Question

Convert the following complex number into its polar representation: -4

A. -4 (cos0 + isin0)
B. -4 (cos pi/2 + isin pi/2)
C. 4 (cos 3pi/2 + isin 3pi/2)
D. 4(cos pi + isin pi)

Answer 1

A and D are basically the same arent they? or is the outside number need to be postive?

Answer 2

for A the 4 is negative for D the 4 is positive

Answer 3

sin0=0; sinpi=0 giving us

-4(cos0) and 4(cospi)

cos0=1 and cospi = -1

Answer 4

im just wondering if there is a "proper" way to express it, maybe the 4 needs to be positive to be "proper"? i cant recall

Answer 5

yes I don't know I really don't get this that's why

Answer 6

if you have some study material (a textbook perhaps) it would better define the "proper" notation

Answer 7

this is an SAT question I'm studying for this so I don't remember anything

Answer 8

http://www.intmath.com/complex-numbers/4-polar-form.php

hmmm, it says the "r" is an absolute value, so id most likely go with the positive 4 as "proper"

Answer 9

so the answer has to have a positive 4 in it?

Answer 10

yes

Answer 11

do you know how can i figure out the rest though?

Answer 12

id hope you can figure it out by the other postings that i have provided ....

Answer 13

-4 is equal to complex value -4+i0, or 4(-1+i0)

Answer 14

and using that to compare with the answers we need it such that

cos(n) = -1
and
sin(n) = 0

Answer 15

so the answer is D?

Answer 16

correct :)

Answer 17

Thank you ! :)

Answer 18

good luck ;)